Morphological Forms of α‐Alumina Particles Synthesized in 1,4‐Butanediol Solution

Phase‐pure, monodispersed, hexagonal plates of single‐crystal α‐alumina (∼ 2 μm wide and ∼0.5 μm thick) have been prepared via precipitation by treating an aluminum hydrous oxide precursor in 1,4‐butanediol at 300°C under autogenous vapor pressure. Present work shows that KOH is the only reagent that precipitates an aluminum hydrous oxide precursor suitable to synthesize α‐alumina in 1,4‐butanediol solution. In contrast, the use of NaOH or NH 4 OH as the precipitating reagent for the precursor material does not yield the alpha phase. The solution pH at which the precursor materials are precipitated is also a critical factor for the formation of α‐Al 2 O 3 . Phase‐pure α‐alumina powders were also only synthesized from the aluminum hydrous oxide precursors precipitated in the pH range from 10 to 10.5. The results of X‐ray diffraction and scanning electron microscopy indicate that longer reaction times promote the phase transformation from the intermediate boehmite phase to α‐alumina. The complete transformation from boehmite to α‐alumina requires reaction times of about 12 h.